Barely a week ago, Mirantis and IBM's SoftLayer division announced their bare-metal-as-a-service hosting plan, Mirantis OpenStack Express. Now Rackspace follows suit with its own similarly themed service, OnMetal, also powered by OpenStack APIs.

The idea behind OnMetal is to allow a user to provision single-tenant, bare-metal servers with the same OpenStack API set that Rackspace uses for its own cloud. The servers are "opinionated" designs (Rackspace's own word) that borrow ideas from the Open Compute Project, of which Rackspace is a member. All OnMetal servers use solid-state storage, have no moving parts, and use only external cooling.

In a blog post, Rackspace described how multitenanted architectures bring with them not just poorer performance, but a more complex operating environment. Applications have to be engineered, Rackspace claims, to deal with the unpredictable performance caused by multitenancy. InfoWorld's tests have borne this out: Amazon EC2, for instance, has deeply unpredictable performance.

In addition, Rackspace seems to be avoiding the overproliferation of machine types, another Amazon.com hallmark. Right out of the gate, Rackspace is offering only three OnMetal machine types: high CPU, high RAM, and high I/O. Those options provide machines with 12 to 20 cores, 32GB to 512GB of RAM, and either a 32GB local boot device or that plus 3.2TB of PCEe Flash storage.

Unlike Mirantis's OpenStack Express, OnMetal isn't actually available yet -- it's scheduled to roll out in late July -- and no firm pricing has been announced. Based on the wording in Rackspace's own blog posts, it sounds like the pricing for OnMetal will be similar to that of other cloud services, with a per-hour rate. There's also little word about prebuilt machine images, but CoreOS, the Docker-based Linux distribution, will be offered as an OS option at launch time.

Without more details about pricing, it'll be hard to say how competitive Rackspace's offering will be. OpenStack Express's pricing is deeply simplified: $60 a day for two servers, with another $30 for each addition. That works out to a cost of around $2.50 an hour. Mirantis's per-node hardware complement is fixed -- a single 16-core CPU, 64GB of RAM, and 500GB of storage -- but it starts at a higher level than the baseline OnMetal offering.

Offering bare metal as a service isn't new. Rackspace and SoftLayer both had similar offerings as of 2012, with both performance and security as major selling points. What's new, though, is the way OpenStack's APIs and infrastructure are used as the provisioning and management model in lieu of a proprietary method -- something that may allow for the kind of automation designed to keep bare metal from being so, well, bare.